Enhancing copper electromigration resistance with indium and oxygen lamination

ABSTRACT

A process and structure for enhancing electromigration resistance within a copper film using impurity lamination and other additives to form intermetallic compounds to suppress metal grain boundary growth and metal surface mobility of a composite copper film. The present invention provides an alloy seed layer and laminated impurities to incorporate indium, tin, titanium, their compounds with oxygen, and their complexes with oxygen, carbon, and sulfur into other films. The intermetallics form and segregate to grain boundaries during an annealing process to reduce copper atom mobility. A further aspect of the present invention is the use of high-temperature, inter-diffusion of additives included in an alloy seed layer to form a barrier layer by combining with materials otherwise unsuitable for barrier material functions.

FIELD OF THE INVENTION

The present invention relates to a process and structure for producingelectromigration-resistant interconnect films used in semiconductorchips and packages. More particularly, the present invention is relatedto processes and structures used to enhance the electromigrationresistance of plated metal interconnect films, such as electroplatedcopper, by enhancing the microstructure of metal films formed for use inchip wiring and packaging applications. Indium, tin, titanium, theircompounds with oxygen, and their complexes with oxygen, carbon, andsulfur are incorporated into the films to suppress metal grain boundarygrowth and metal surface mobility.

BACKGROUND OF THE INVENTION

Aggressive device scaling and interconnection ground rules arechallenging the physical limits of materials, processes, and structuresin the semiconductor industry. For wiring patterns formed onsemiconductor chips and packages, copper has emerged as the metallurgyof choice because of various beneficial properties. Despite the variousadvantages of copper, the electromigration lifetime of a copper filmdepends strongly on the processes used to form the copper film. Forexample, the activation energy required to create failures, due toelectromigration of a copper film, typically ranges from 0.7 to 1.0 eV.It is desirable to produce a copper-containing film in which theactivation energy required to cause failure is increased beyond 1.3 eV.It is further desirable to produce such a film without major processingmodifications and without the addition of multiple processing steps. Itis also desirable to produce such a film without bringing about anyperformance degradation.

The thermo-mechanical, electrical, and metallurgical properties,microstructure, and etching characteristics of a film depend on theprocess used to produce the film. More specifically, these qualitiesdepend upon the microstructure of the metal film so produced. Themicrostructure of the metal film is enhanced when dopant impuritymaterials are disposed along the grain boundaries of the film. Theseimpurities help to suppress grain growth and grain recovery within thefilm. Uncontrolled grain recovery and grain growth may cause defectsduring subsequent processes, in addition to compromising the qualitiesnoted above.

The presence of partially soluble and insoluble intermetallic materialswithin a heat-treated metal film produce a microstructure which includesa high twinning density (multiple twins per grain). These intermetallicmaterials will be preferentially segregated along grain boundary regionsand near the surface of the copper-containing film. The presence ofthese partially soluble and insoluble intermetallic materials, alongcopper grain boundaries and near the copper surface, reduces coppergrain boundary mobility and the mobility of copper atoms along thesurface. The interaction of the impurities and the high twinning densityformed within the copper microstructure enhances the electromigrationlifetime of the entire film structure being used as an interconnectmaterial. This enhancement occurs because such a structure requires moreenergy to cause atomic migration preferentially in any given direction.Electromigration failures happen when significant atomic migrationoccurs preferentially in one direction.

What is needed is an improved process and structure, for producing acopper film used as a wiring interconnection material, offeringincreased resistance to electromigration failures.

SUMMARY OF THE INVENTION

The present invention addresses the shortcomings of the conventional artby replacing the conventional seed layer used in electrodepositionprocesses with an alloy seed is layer having a copper alloy which mayinclude copper, indium, tin, titanium, and chromium. After the seedlayer is formed on a substrate, a copper film is formed on the seedlayer. Within or on top of the bulk copper film, an impurity film withcomparatively large amounts of impurities such as oxygen, sulfur,nitrogen, and carbon is laminated. After the in-situ impurityelectro-lamination is completed, additional films may be added to form acomposite interconnect film which includes copper. After the compositefilm structure is completed, the substrate is annealed. During theannealing process, impurity compounds such as indium oxide, tin oxide,and their complexes are formed as the additives from the alloy seedlayer combine with the oxygen, for example, included in the highimpurity content laminated film.

The presence of high temperature intermetallic compounds such as indiumoxide and other oxides, segregated to the grain boundaries of the copperfilm, dramatically reduces grain boundary and surface diffusion andmobility. This reduction in copper atom mobility increases theelectromigration resistance and the electromigration lifetime of a newlyformed copper-containing film. A further aspect of the present inventionis the use of high temperature inter-diffusion of an additive, includedin an alloy seed layer, to form a barrier layer by combining withmaterials otherwise unsuitable for barrier material functions. Theaddition and formation of such a barrier material improves variouselectromechanical aspects of the film formed.

The present invention provides various processes and structures whichimprove the electrical, metallurgical, thermo-mechanical, and otherproperties of copper-containing films. By its nature, copper has a shortelectromigration lifetime. A pure copper film is highly susceptible torapid grain growth and particularly high surface mobility atcomparatively moderate temperatures. One process of the presentinvention to enhance the electromigration of a copper thin film is toadd impurities, which retard grain growth and surface mobility. Apreferred process for accomplishing this result is to laminateimpurities into the structure of a deposited metal film. The laminatedimpurities within the metal interact, in turn, with other species in themetal composite film to form high temperature compounds. The hightemperature compounds are not readily soluble in copper; rather, theysegregate preferentially to copper grain boundaries where they retardgrain boundary growth and copper surface mobility during the applicationof electromotive forces. This retardation increases the electromigrationlifetime of the film.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF THE DRAWING

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures.

FIG. 1 through FIG. 7 are cross-sections showing the process sequenceused to form an exemplary embodiment of the present invention. Morespecifically,

FIG. 1 is a cross-sectional view showing a substrate after an alloy filmhas been added;

FIG. 2 is a cross-section showing a copper-containing film added to thestructure of FIG. 1;

FIG. 3 is a cross-section showing a roughened surface formed on thecopper-containing film;

FIG. 4 is a cross-section showing a high impurity content film laminatedonto the copper-containing film;

FIG. 5 is a cross-section showing the structure after a furthercopper-containing film has been added;

FIG. 6 is a cross-section showing the structure as in FIG. 5 after ithas been heat-treated; and

FIG. 7 is a cross-section showing a composite metal film of oneexemplary embodiment of the present invention.

FIGS. 8A, 8B, 8C, and 8D are cross-sectional views showing varioussubstrate structures onto which the composite film of the presentinvention may be formed.

FIG. 9 and FIG. 10 are cross-sections showing two different structuresformed according to another exemplary embodiment of the presentinvention, with FIG. 9 illustrating a cross-sectional view of acomposite film structure including two bulk deposited films and FIG. 10illustrating a cross-sectional view of a composite film including onebulk deposited film.

FIGS. 11 through 15 are cross-sectional views showing the processsequence used to form another exemplary embodiment of the presentinvention. More specifically,

FIG. 11 is a cross-sectional view showing an alloy seed layer filmformed on a substrate;

FIG. 12 is a cross-sectional view showing a roughened surface formed onthe alloy seed layer;

FIG. 13 is a cross-sectional view showing the structure after alaminated impurity film and a bulk metal film have been added;

FIG. 14 is a cross-sectional view showing the effects of heat-treatingthe structure; and

FIG. 15 is a cross-sectional view showing a composite film of anotherexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention is directed generally to formingmultiple films in sequence to form a single composite film structure. Inthe preferred embodiment, a bulk metal film is formed by electroplating,but other suitable processes for depositing a metal film may be used.Before the formation of the bulk metal film, the present inventionincludes the formation of an electroplating seed layer which includescopper and an additive. An electroplating solution may be used to form asurface microstructure which includes high crystallographic index planeson the bulk film or films. In addition, a film with a high impuritycontent may be laminated onto the microstructure of the surface whichforms the interface between sequentially deposited metal films. Thishigh impurity content laminated film may be formed from the sameelectroplating solution used to form a bulk film.

Heat treating processes urge the diffusion of the additive from thealloy seed layer and the interaction between the additive from the seedlayer and further additives or impurities such as the interaction withimpurity materials from the laminated impurity film. In this manner, theadditives from the alloy seed layer can be used to form compounds alongcopper grain boundaries which enhance the electromigration resistance ofthe film, or they may combine with other materials, which wouldotherwise be unsuited for barrier layer purposes, to form an effectivebarrier layer.

The composite copper-containing films formed according to the process ofthe present invention may be patterned to serve as interconnection wiresfor application in semiconductor chips or packages. There are at leastthree well-known procedures for forming such a wiring pattern from thecomposite films formed according to the various examples of the presentinvention. One such example for forming a pattern includes the"plate-through" process.

In the plate-through process, a photoresist pattern is formed on asubstrate. Next, the sequence of films is deposited selectively on areasof the substrate surface which are not masked by photoresist. After thecomposite film is formed, the photoresist is removed thus producing awiring interconnection pattern of the composite metal film.

The second commonly used process includes providing a substrate, thenforming the composite copper-containing film on the substrate. After thecomplete composite film is formed, a photoresist pattern is created ontop of the composite film. Next, etching processes are used to removethe exposed sections of the composite film which are not protected bythe photoresist pattern thereby producing the wiring interconnectionpattern. The photoresist is then removed.

A third and most favored procedure used in the modern processingindustry includes the damascene process for forming interconnectionpatterns. In the damascene process, an insulating dielectric material isformed on the substrate and grooves are formed to create a patternwithin the material. The composite metal film is then formed on thedielectric material, filling the trenches formed within the dielectricmaterial. After the composite film formation is complete, the overburdenof the composite metal film is removed from the upper surfaces of thedielectric material, thereby producing a wiring pattern of the compositemetal film which remains within the trenches.

It should be understood by one skilled in the art that the compositefilm structures produced, according to the process of the presentinvention, may be subsequently formed into wiring patterns by either ofthe above three processes. In addition, any other process known to theart, to create a wiring pattern from a composite metal film, may beused. As such, the exemplary embodiments of the present invention willnot be described in conjunction with any specific process for forming awiring pattern using the composite film of the present invention.

The following examples are included to more clearly demonstrate theoverall nature of the invention. These examples are exemplary, notrestrictive, of the invention.

Example 1 Combination with Laminated Impurities

In this exemplary embodiment of the process used to form the compositecopper-containing film of the present invention, the composite film isformed upon a substrate. Referring to FIG. 1, the substrate 2 may be asemiconductor wafer in the preferred embodiment. A dielectric insulatinglayer 8 may be formed on the semiconductor substrate 2. In the preferredembodiment, a barrier layer film 4 may be formed on the dielectric layer8. The barrier layer film 4, however, is not required. When a barrierlayer film 4 is used, any suitable barrier material may be used.Likewise, any procedure common to the art may be used to form thebarrier layer film 4 on the dielectric layer 8 which is formed onsubstrate 2.

Next, a plating base film is formed on the substrate 2. The plating basefilm comprises a copper alloy seed layer 6 which may includecopper-indium, copper-tin, copper-titanium, or copper-chromium. Theconcentration of the indium, tin, titanium, or chromium additive withinthe alloy may lie within the range of 0.01 to 5.0 atomic percent, butpreferably is between 0.08 to 3 atomic percent. Any process suitable inthe art to form the alloy seed layer 6 may be used. For example, thealloy seed layer 6 may be formed through evaporation, sputtering,co-sputtering, immersion-plating, and electroplating processes. Thethickness of the copper alloy seed layer 6 may range from 100 to 3,000angstroms and, in the preferred embodiment, may range from 250 to 1,800angstroms. Copper alloy seed layer 6 has a surface 7.

After the barrier layer film 4 and the copper alloy seed layer 6 havebeen formed on the semiconductor substrate 2, the substrate 2 mayrequire an initial cleaning operation before the deposition of the bulkcopper-containing film. The necessity of the cleaning operation isdetermined by the cleanliness of the substrate 2 and also the thicknessand composition of the copper alloy seed layer 6: the copper alloy seedlayer 6 will be partially etched, during the cleaning operation, and theimpurity additive within the copper alloy seed layer 6 may bepreferentially etched.

The semiconductor substrate 2 may cleaned by etching in a sulfuric acidsolution. The sulfuric acid concentration of the cleaning solution mayrange from 1 percent to 15 percent sulfuric acid in de-ionized water,but preferably may be within the range of 2 to 8 percent. The immersiontime in the sulfuric acid solution may vary from 0 to 30 seconds, mostpreferably less than 10 seconds. This immersion is followed by rinsingin de-ionized water before the formation of the bulk copper-containingfilm. When the copper alloy seed layer 6 is thin and the substrate 2 isalready sufficiently clean, this pre-cleaning step before formation ofthe bulk film may be bypassed.

Now turning to FIG. 2, a bulk copper-containing film 10 is deposited onthe top of copper alloy seed layer 6. Bulk copper-containing film 10 hasan exposed surface 11. The bulk copper-containing film 10 may bedeposited by electroless plating, physical vapor deposition (PVD),chemical vapor deposition (CVD), or electroplating processes or variouscombinations of these processes.

In the case of electroplating, the substrate is electroplated in asuitable electroplating bath, containing impurity additives, as follows.The substrate is immersed in a plating cell in which the platingsolution may be agitated with respect to the substrate. The substratemay be exposed to the plating solution for a brief period of time beforethe application of an electrical potential to the substrate. This briefdwell time may vary from 0 to 20 seconds but, in the preferredembodiment, may be within the range of 0 to 10 seconds. During this timeperiod, the substrate may be preferably rotated at 10 to 400 rpm.

When an acid copper plating bath is used, in addition to copper sulfatepentahydrate and sulfuric acid, other additives may be included such aschloride ions, MD, and ML_(o). MD and ML_(o) are commercially availableplating bath additives common in the plating industry. The coppersulfate pentahydrate concentration within the solution may vary from 20to 130 grams/liter. In the preferred embodiment, the concentration rangelies within 35 to 110 grams/liter. The sulfuric acid content of the bathmay range from 100 to 230 grams/liter and, in the preferred embodiment,the sulfuric acid content ranges from 150 to 210 grams/liter.

With respect to chloride ions as additives, the plating bathconcentration may vary from 25 to 180 parts per million, and lies withinthe range of 45 to 130 parts per million in the preferred embodiment.With respect to additive MD, the concentration may range from 2 to 18milliliters/liter and, in the preferred embodiment, is within the rangeof 4 to 16 milliliters/liter. With respect to the concentration ofadditive ML_(o) within the bath, the concentration range of thepreferred embodiment is between 0.5 to 3.5 milliliters/liter, but mayrange from 0.3 to 4.5 milliliters/liter.

After the brief dwell period within the plating solution, the platingprocess is initiated. During the plating process, the electroplatingcurrent density may range from 5 to 60 MA/cm². In the preferredembodiment, this current density may range from 10 to 40 mA/cm² and mostdesirably within the range of 10 to 30 mA/cm². The anode material usedmay consist of a CuP alloy, as typically used in copperelectrodeposition. The plating surface of the substrate may be platedfacing downward, and rotation may be used as an additional source ofagitation during the electroplating process. The substrate may berotated at a rate of 10 to 500 rpm, but most preferably within the rangeof 10 to 180 rpm. In the preferred embodiment, the desired rotation ratewill range from 30 to 120 rpm during the plating operation. Theelectrodeposition is carried out by rendering the substrate a cathodefor 5 to 40 seconds, preferably 5 to 30 seconds, to form anelectroplated film which will comprise one layer of the composite filmof the present invention, and is shown as bulk copper-containing film 10in FIG. 2.

The impurity content of the various additives formed within theelectrodeposited, bulk copper-containing film 10, may be as follows:

    ______________________________________                                                            Preferred Impurity                                          Impurity Content Content                                                    ______________________________________                                        Carbon      3-120 ppm   3-75 ppm                                                Oxygen 0-100 ppm 0-30 ppm                                                     Chlorine 2-200 ppm 2-100 ppm                                                  Nitrogen 0-100 ppm 0-30 ppm                                                   Sulfur 1-60 ppm 1-15 ppm                                                    ______________________________________                                         Table 1. Impurity Concentration in the Plated Film (in parts per million)

The formation of the composite film of the present invention iscontinued by performing a spin-and-etch operation to roughen surface 11of bulk copper-containing film 10. As above, bulk copper-containing film10 may be formed in alternative embodiments by electroless plating, PVD,CVD, or other suitable processes for the formation of metal films. Inthe alternative embodiments, the process is continued by contacting thebulk copper-containing film 10 with the same electroplating solution asdescribed in conjunction with the preferred embodiment ofelectrodeposition. In the preferred embodiment, the substrate is removedfrom the electroplating solution.

In either embodiment, with the electroplating solution disposed on thesurface of the substrate, the substrate is next spun at a rate of 20 to1800 rpm, preferably in the range of 300 to 1200 rpm, to completely spinthe plating solution off the substrate surface. The spin time may rangefrom 5 to 60 seconds and, in the preferred embodiment, may be 10 to 50seconds. This operation also simultaneously etches a uniquemicrostructure onto the substrate surface. The presence of oxygen in theambient environment, within which this spinning operation is performed,accelerates the creation of the unique microstructure formed within theexposed copper-containing film surface. In the preferred embodiment, theoperation takes place in air, but other oxygen-containing environmentsmay be used.

As shown in FIG. 3, a surface 11' having a roughened microstructure isproduced on exposed surface 11 of bulk copper-containing film 10.Surface 11' has an extremely large micro-surface area. This spin-offprocess and etching operation also expose high crystallographic indexplanes in the plated copper film.

Now turning to FIG. 4, after the spin-off and etching operation has beencompleted, the substrate is next submerged into the electroplatingsolution. Before electroplating current is applied, however, thesubstrate is re-introduced into the plating solution and rotated using arotation rate of 5 to 400 rpm. In the preferred embodiment, the rotationrate may range from 10 to 90 rpm for a period of 2 to 30 seconds. In thepreferred embodiment, this dwell time will be within the range of 2 to20 seconds. During this time, a minimal current of 3 to 5 mA/cm², whichis much less than the electroplating current, may be applied, or thesolution may be maintained in an electrically neutral state during thislamination step. During this dwell period before the electroplatingcurrent is applied, the additives from the bath adsorb onto the largemicro-surface area and the high crystallographic planes created onsurface 11' by the prior step.

In this manner, an impurity film 13 is laminated onto the first bulkcopper-containing film 10 of the composite film of the presentinvention. More specifically, an impurity film 13 is laminated onto thesurface 11' formed on the surface of the first deposited bulkcopper-containing film 10. The additives contained in the platingsolution are preferentially absorbed from the solution and onto thecopper microstructure of surface 11' during this lamination process.Thus, a thin film containing an increased impurity content is laminatedonto the microstructure to provide a discrete region of high impurityconcentration within a composite film structure. This region of highimpurity concentration has a higher impurity concentration than acorresponding impurity concentration within a bulk film produced byelectroplating from the same electroplating solution.

The concentration of impurities, within the laminated impurity film 13produced on surface 11' within the composite copper-containing film, mayvary from the concentration of an impurity within a bulkelectrodeposited film formed from the same electroplating solution (asin Table 1), up to sub-monolayer values. In the preferred embodiment, inwhich the first bulk electrodeposited film includes impurities from theelectroplating bath, the concentration of the same impurities formedfrom the same electroplating bath within the laminated impurity filmwill be significantly greater. The maximum concentration range ofimpurities such as carbon, oxygen, nitrogen, and sulfur is approximately1×10¹³ to 1×10¹⁴ atoms/cm².

Now turning to FIG. 5, after this brief dwell period during whichimpurity film lamination occurs, and while still in the electroplatingsolution, an electroplating current is applied to the cathode to formanother electrodeposited bulk copper film 15 and to continue the filmformation process. The electroplating time is determined by the requiredtotal film thickness of the composite film. The electroplating processdetails may be the same as described above in conjunction with theformation of bulk copper-containing film 10. Likewise, the filmcharacteristics of the electroplated film 15 such as the impuritycontent will also be as described in conjunction with bulkcopper-containing film 10. Through the use of the described operatingsequence of film formation, spin and etch, dwell, and electroplate, afilm having a high concentration of impurity such as carbon, oxygen,sulfur, and nitrogen is laminated within the composite copper film.

Now turning to FIG. 6, composite film 25 includes barrier film 4, copperalloy seed layer 6, bulk copper-containing film 10 with roughenedsurface 11', laminated impurity film 13, and electrodeposited bulkcopper film 15. After the substrate is removed from the electroplatingsolution and dried, composite film 25 is next annealed. In an exemplaryembodiment, the substrate may be rinsed after removal from theelectroplating solution and prior to drying. The annealing process takesplace in an inert ambient environment such as nitrogen, forming gas, orhydrogen. The annealing times may range from 2 to 180 minutes and, inthe preferred embodiment, they may range from 5 to 150 minutes. In thepreferred embodiment, the temperature range may vary from 100 to 500°C., but temperatures as high as 600° C. may be used. As the temperatureis increased, the necessary time for the annealing process to occur willbe decreased accordingly. According to one exemplary embodiment,composite film 25 may be annealed at a temperature within the range of250° C.-500° C. at a time within the range of 30 to 60 minutes.

During the heat treatment, the minor components of the alloy seed layer6 such as indium, tin, titanium, chromium, or other species, which willdiffuse faster than copper atoms, diffuse away from the alloy seed layer6 and form intermetallic materials. This diffusion is shown as arrows 20in FIG. 6. As shown by arrows 20, these species diffuse away from thealloy seed layer 6 and toward the electro-laminated impurities containedin impurity film 13. These materials from the copper alloy seed layer 6interact with the impurities contained in laminated impurity film 13 toform chemical compounds and complexes such as indium oxides, tin oxides,Cu--In--O complex, Cu--Sn--O complex, chromium oxides, titanium oxides,aluminum oxides, and various other complexes depending on the additivesand impurities used.

Although oxygen may be the preferred impurity species contained withinlaminated impurity film 13, carbon, nitrogen, and sulfur may beadditionally or alternatively used in alternate embodiments. As such,chemical compounds and complexes including carbon, nitrogen, and sulfurmay also be formed from the interaction between the additive materialfrom the alloy seed layer 6 and the impurity contained in impurity film13. Arrow 18 of FIG. 6 represents the direction of travel of theimpurity species from laminated impurity film 13, as the speciesdiffuses to interact with the additive from the alloy seed layer 6. Thedirection and path of diffusion, as well as the location of thecompounds and complexes formed, will be along the grain boundaries ofbulk copper-containing film 10.

Now turning to FIG. 7, the first embodiment of composite film 25 of thepresent invention includes the compounds and complexes as above whichare formed during the heat treatment process. The interstitial locationsof these compounds and complexes, formed along the grain boundaries, arepreferentially in region 22 which is nearer the laminated impurity film13 than the surface 7 of alloy seed layer 6. The compounds tend to formtoward the exposed surface 26 of the composite film 25 and away fromsubstrate 2. As the annealing temperature is increased, the formedcompounds may be disposed between original impurity film 13 and exposedsurface 26 as the location of region 22 moves closer to exposed surface26.

The presence of the partially soluble and insoluble intermetallicmaterials in the heat-treated, deposited, metal, composite film 25produces a microstructure which includes high twinning density (multipletwins per grain) and includes the intermetallics preferentially locatedalong the grain boundary regions near the copper composite film surface26. The presence of these intermetallic materials, along copper grainboundaries and near the surface 26, reduces copper grain boundary growthand copper atom surface mobility. The interaction of the impurities andthe high twinning density within the copper grain structure enhance theelectro-migration lifetime of the entire interconnect composite film 25.The composite film 25 as formed will require a greater amount of energyto cause a majority of copper atoms to migrate preferentially in anygiven direction, and hence to cause electromigration failures.

The composite film 25 may be formed into a pattern by use of any of themechanisms as described above. The composite film may be formed on asubstantially flat surface and patterned thereafter, or it may be inlaidwithin a trench or other damascene structures. Typical examples ofpatterning processes appear in FIGS. 8A, 8B, 8C, and 8D. FIG. 8A shows across-section of an embodiment in which the damascene patterning processis used. A trench 35 is formed within the dielectric layer 8 formed onsubstrate 2. The composite metal film 25 of the present invention isformed over exposed surfaces 31 which include the side walls 34 andbottom surface 38 of the trench 35, and the top surface 32 of thedielectric film B. A pattern, including the portion of composite film 25disposed within trench 35, may be is formed using conventional damasceneprocesses.

FIG. 8B shows a cross-section of the composite film 25 of the presentinvention formed on the dielectric layer 8 on the substrate 2.Photoresist pattern 33 is formed on top surface 26 of composite film 25.Conventional etching mechanisms may be used to remove the portions ofcomposite film 25 which are in the exposed region 37. After etching iscomplete, photoresist 33 may be removed by any suitable process typicalin the art.

FIG. 8C shows application of the present invention to form compositefilm 25 using the "plate-through" process of patterning. In thisapplication, a photoresist pattern 33 is formed on the dielectricmaterial 8 on the substrate 2. Next, the remaining layers of thecomposite film 25 of the present invention are selectively formed onexposed surface 31. After the composite film 25 is formed, photoresist33 may be removed by any suitable process typical in the art, to producea pattern within composite film 25.

FIG. 8D shows a cross-section of an embodiment in which a damascenepatterning process is used with a dual damascene structure. A trench 35is formed within the dielectric layer 8 formed on substrate 2. Thecomposite metal film 25 of the present invention is formed over exposedsurfaces 31 which include the side walls 34, lip sections 39, and bottomsurface 38 of the trench 35, and the top surface 32 of the dielectricfilm 8. A pattern, including the portion of composite film 25 disposedwithin trench 35, may be formed using conventional damascene processes.

Example 2 Multiple Alloy Seed Layers

A further aspect of the present invention is directed to a process forproducing multiple metal layers having different microstructures ortextures. Referring to FIG. 9, the composite film 30 includes an alloyseed layer 6, a bulk deposited copper-containing film 10, and alaminated impurity film 13 all as described in conjunction withExample 1. In the preferred embodiment, a barrier layer film 4 may alsobe included. The barrier layer film 4 is disposed between the dielectricfilm 8 on substrate 2 and the first alloy seed layer 6. In thisexemplary embodiment, bulk copper-containing film 10 may be formed usingprocesses such as PVD, CVD, electroless plating, and others. In thepreferred embodiment, electrodeposition is used to form bulkcopper-containing film 10.

After high impurity content impurity film 13 has been formed overroughened surface 11', a second alloy seed layer 27 is formed. Thesecond alloy seed layer 27 may be deposited by immersion plating,electroless plating, PVD, CVD, or other metal deposition processes. Inthe preferred embodiment, this second alloy seed layer 27 may becomprised of a copper tungsten alloy, a nickel phosphorus alloy, aCoP/NiP alloy, or an immersion tin layer. In alternate embodiments,other materials may also be suitable. The thickness of this second alloyseed layer 27 may range from 25 to 500 angstroms, but will range from 25to 200 angstroms in the preferred embodiment.

Second bulk film 29 is formed over second alloy seed layer 27. Secondbulk film 29 is comprised of copper is and is formed by electroplatingin the preferred embodiment. In an alternate embodiment, second bulkfilm 29 may comprise gold, a Pb--Sn alloy, other solderable alloys, orother materials. After formation, the composite metal film structure isannealed. The annealing takes place in an inert ambient. During thisheat-treatment step, additive materials from the first alloy seed layer6 diffuse through first deposited bulk copper-containing film 10 andinteract with the impurities contained within laminated impurity film13, materials from second alloy seed layer 27, or both to formintermetallics. As described in conjunction with the first example, theimpurity species contained within laminated impurity film 13 may beoxygen in the preferred embodiment, but may be nitrogen, sulfur, carbon,or other materials in an alternative embodiment.

Example 3 Second Alloy Seed Layer Followed by Annealing

Now turning to FIG. 10, another exemplary embodiment of the presentinvention may include the second alloy seed layer 27 and the underlyingstructure as described in conjunction with Example 2, but will notinclude any subsequently deposited film over the top surface 28 of thesecond alloy seed layer 27. Rather, after formation of second alloy seedlayer 27, the structure is subjected to heat treating. In the preferredembodiment, this second alloy seed layer 27 may be comprised of a coppertungsten alloy, a nickel phosphorus alloy, a CoP/NiP alloy, or animmersion tin layer. In alternate embodiments, other materials may alsobe suitable.

The heat-treatment step may be the annealing process as described above,in the preferred embodiment. During the heat-treatment step in anambient environment, fast-diffusing atomic species from the lower firstalloy seed layer 6 diffuse through first bulk copper-containing film 10and toward laminated impurity film 13 and second alloy seed layer 27.Impurities such as indium, tin, titanium, and chromium from first seedlayer 6 interact with the laminated impurities within film 13, impurityspecies from second alloy seed layer 27, or both to form intermetallicmaterials including compounds and complexes. The intermetallic materialswill be formed in or near the regions of the laminated impurity film 13and second alloy seed layer 27. The presence of these intermetallicmaterial compounds or complexes near the surface of the bulkcopper-containing film 10 suppresses the surface mobility of coppergrains, thus enhancing the electromigration resistance of the compositestructure.

Example 4 In-situ Barrier Film Formation

Another example of the present invention is directed to a process forforming a barrier film in-situ on a semiconductor substrate or packagingstructure. This process of the present invention allows for the use ofmaterials which by their nature may not otherwise be suitable barriermaterials. By disposing these typically unsuitable barrier materials ina location whereby films of other materials may be deposited adjacent tothem, these unsuitable barrier materials may interact or complex withmaterials from the adjacent films to form a new material which possessesadequate barrier properties.

Now referring to FIG. 11, substrate 52 has a dielectric material 58 andan alloy seed layer 56 disposed on substrate 52. The alloy seed layer 56is a copper alloy including copper and indium, chromium, titanium, ortantalum as the minor component within the alloy. The concentration ofthe minor component within the alloy may vary from 0.2 to 10 atomicpercent. In the preferred embodiment, the concentration may lie between0.2 to 5 atomic percent. The thickness of the alloy seed layer 56 mayrange from 10 to 200 angstroms, but will lie within 10 to 150 angstromsin the preferred embodiment.

The alloy seed layer 56 may be sputtered from a master alloy target inthe preferred embodiment. In an alternative embodiment, the alloy seedlayer 56 may be formed by co-sputtering, sputtering, co-evaporation,evaporation, immersion plating, electroplating, or other processes. Overthe alloy seed layer 56, a copper seed layer 60 is formed. The copperseed layer 60 may be formed by sputtering or CVD (chemical vapordeposition) processes. The thickness of the copper seed layer 60 mayrange from 50 to 1,500 angstroms, and in the preferred embodiment willrange between 100 and 1,000 angstroms. Copper seed layer 60 has anexposed surface 57.

Now turning to FIG. 12, the surface 57 of the copper seed layer 56 ismodified in a suitable electroplating bath by the spin-etch process, asdescribed in conjunction with Example 1, to form a roughened surface57'. Roughened surface 57' has exposed, high-index crystallographicplanes.

As shown in FIG. 13, a high impurity content film 62 is next laminatedonto roughened surface 57'. The procedure for forming the high impuritycontent film 62 is as described in conjunction with Example 1.Impurities which may be laminated onto the structure in this processinclude carbon, sulfur, oxygen, nitrogen, and, in the preferredembodiment, a combination of oxygen, nitrogen, and carbon. A bulkcopper-containing film 64 is then electrodeposited over the laminatedhigh impurity content film 62. Any suitable process for electroplatingwhich is known in the art may be used for this purpose.

Now turning to FIG. 14, the composite structure 70 is then annealed. Theannealing process takes place in an inert ambient such as air ornitrogen, at temperatures ranging from 100 to 550° C., and preferablywithin the range of 200 to 500° C. The annealing time may range from 10minutes to 3 hours, and in an exemplary embodiment may range from 30minutes to 180 minutes. During this heat treatment, the laminatedimpurities from high impurity content film 62 interact with thematerials in the alloy seed layer 56. Arrows 66 represent the directionof inter-diffusion between the materials of the respective films. Thisinteraction of materials from respective films results in the formationof a barrier material.

The heat treatment produces barrier film 68 as shown in FIG. 15. In thismanner, a barrier film 68 with adequate barrier layer properties hasbeen formed, in-situ, from materials which otherwise would be unsuitablefor barrier purposes. Examples of barrier materials formed in thismanner include Cu(O), CuTiO, CuCr(O), and their complexes with nitrogen,carbon, or sulfur. Other barrier materials may be produced, depending onthe additives incorporated into the seed layer (56 in FIG. 11) and theimpurities added via laminated high impurity content film 62 in FIG. 13.In the composite film structure 70, the composite film includes bulkcopper-containing film 64 and barrier film 68. FIG. 15 shows thiscomposite film disposed upon a semiconductor substrate 52.

As with the previous embodiments, after the composite film structure iscompleted, a pattern is formed within the film to produce a wiringpattern. In the preferred embodiment, one of the processes forpatterning, as described previously, may be used to form the pattern.Any suitable process may be used, however, for forming a pattern of acomposite metal film.

Although the invention is illustrated and described above with referenceto specific embodiments and examples, the invention is not intended tobe limited to the details shown. Rather, various modifications andadditions may be made in the details within the scope and range ofequivalents of the claims and without departing from the invention. Theprocesses and films described above may be used in various combinationsto form a number of composite copper-containing films with desirablethermo-mechanical, electrical, and metallurgical properties. Theimpurities introduced and disposed within the composite film structurealso provide a composite copper-containing film with superiorelectromigration resistance. The processes could be used in conjunctionwith other platable materials, such as Au, Ni, Cr, and other materialsused to fabricate structures for semiconductor packaging, or other hightemperature applications.

The details of the processes used to form the structures of the presentinvention may also differ, from the process parameters detailed above,and still remain within the scope of the present invention. Furthermore,the final film structure may be varied and remain within the scope ofthe present invention.

What is claimed:
 1. A process for forming a copper-containing film,comprising the steps of:(a) forming a seed layer at least indirectly ona semiconductor substrate, said seed layer including copper and anadditive; (b) forming a bulk copper-containing film on said seed layer,said bulk copper-containing film including associated grain boundariesand an exposed surface; (c) contacting said exposed surface with anelectroplating solution and mechanically removing said electroplatingsolution from said surface within an oxygen environment, therebyroughening said exposed surface; (d) laminating an impurity film ontosaid exposed surface by immersing said substrate in said electroplatingsolution, said impurity film including copper and an impurity and havinga first impurity concentration; (e) forming a further bulkcopper-containing film on said impurity film, said further bulkcopper-containing film including said impurity, a second impurityconcentration, associated grain boundaries, and a further exposedsurface; (f) drying said substrate; and (g) annealing said substrate toform a plurality of compounds disposed along said grain boundaries, themajority of said plurality of compounds including said additive and saidimpurity in combination; wherein said first impurity concentration isgreater than said second impurity concentration.
 2. The process as inclaim 1, further comprising the step (d1) of removing said substratefrom said electroplating solution and drying said substrate.
 3. Theprocess as in claim 1, wherein said bulk copper-containing film furtherincludes said impurity and a third impurity concentration, and saidfirst impurity concentration is greater than each of said secondimpurity concentration and said third impurity concentration.
 4. Theprocess as in claim wherein at least one of said bulk copper-containingfilm or said further bulk copper-containing film is formed by amechanism selected from the group consisting of electroless plating,chemical vapor deposition, and physical vapor deposition.
 5. The processas in claim 1, further comprising the step of forming a wiring patternwithin said copper-containing film as one of step (f1) and step (h). 6.The process as in claim 1, wherein said roughening comprises forminghigh index crystallographic planes within said exposed surface.
 7. Theprocess as in claim 1, further comprising the step of interposing abarrier layer film between said seed layer and said semiconductorsubstrate.
 8. The process as in claim 1, wherein said step ofmechanically removing said electroplating solution comprises spin dryingsaid substrate.
 9. The process as in claim 1, wherein said annealing iscarried out at a temperature within the range of 250° C. to 500° C. at atime within the range of 30 to 60 minutes.
 10. The process as in claim1, further comprising applying an electrical current within the range of3 mA/cm² to 5 mA/cm², to said plating solution during said step oflaminating.
 11. The process as in claim 1, wherein said electroplatingsolution is maintained in an electrically neutral state during said stepof laminating.
 12. The process as in claim 1, wherein said annealing iscarried out in an inert atmosphere, said inert atmosphere comprising oneof forming gas, air, and nitrogen.
 13. The process as in claim 1,wherein at least one of said bulk copper-containing film or said furtherbulk copper-containing film is formed by electroplating.
 14. The processas in claim 13, wherein said electroplating is carried out using saidelectroplating solution.
 15. A process for forming an electrodepositedcopper-containing film, comprising the steps of:(a) forming a seed layerat least indirectly on a semiconductor substrate, said seed layerincluding copper and an additive; (b) immersing said substrate in anelectroplating solution; (c) electrodepositing a first bulkcopper-containing film from said electroplating solution onto said seedlayer, said first bulk copper-containing film including an impurity, afirst impurity concentration, associated grain boundaries, and anexposed surface; (d) removing said substrate from said electroplatingsolution and mechanically removing said electroplating solution fromsaid bulk copper-containing film within an oxygen environment, therebyroughening said exposed surface; (e) laminating an impurity film ontosaid exposed surface by immersing said substrate in said electroplatingsolution, said impurity film including copper, said impurity, and havinga second impurity concentration; (f) electrodepositing a second bulkcopper-containing film from said electroplating solution onto saidimpurity film, said second bulk copper-containing film including saidimpurity, a third impurity concentration, associated grain boundaries,and a second exposed surface; (g) removing said substrate from saidelectroplating solution; (h) rinsing then drying said substrate; and (i)annealing said substrate to form a plurality of compounds disposed alongsaid grain boundaries, the majority of said plurality of compoundsincluding said additive and said impurity in combination; wherein saidsecond impurity concentration is greater than each of said firstimpurity concentration and said third impurity concentration.
 16. Aprocess for forming a copper-containing film, comprising the stepsof:(a) forming a first seed layer at least indirectly on a semiconductorsubstrate, said seed layer including copper and an additive; (b) forminga bulk copper-containing film on said seed layer, said bulkcopper-containing film including an exposed surface; (c) contacting saidexposed surface with an electroplating solution and mechanicallyremoving said electroplating solution from said surface within an oxygenenvironment, thereby roughening said exposed surface; (d) laminating animpurity film onto said exposed surface by immersing said substrate insaid electroplating solution, said impurity film including an impurity;(e) forming a second seed layer at least indirectly on said exposedsurface; and (f) annealing said substrate to diffuse said additivewithin said copper containing film.
 17. The process as in claim 16,wherein said step of forming a bulk copper-containing film comprises oneof physical vapor deposition, chemical vapor deposition, electrolessplating, and electrodeposition.
 18. The process as in claim 16, whereinsaid step of forming a second seed layer comprises one of immersionplating, electroless plating, physical vapor deposition, and chemicalvapor deposition.
 19. The process as in claim 16, wherein saidroughening comprises exposing high crystallographic planes within saidexposed surface.
 20. The process as in claim 16, wherein said impuritycomprises one of carbon, oxygen, nitrogen, and sulfur, and saidannealing causes an interaction between said additive and said impurity.21. The process as in claim 16, further comprising interposing a barrierlayer film between said first seed layer and said semiconductorsubstrate.
 22. The process as in claim 16, further comprising the step(e1) of forming a second bulk film on said second seed layer, andwherein said second seed layer comprises copper and a further additive,and said annealing causes an interaction between said additive and oneof said further additive and said impurity to form an intermetallicfilm.
 23. The process as in claim 22, wherein said step of forming asecond bulk film comprises electroplating.
 24. The process as in claim16, further comprising the step (e1) of forming a second bulk film onsaid second seed layer, and wherein said second seed layer comprisescopper and a further additive, and said annealing causes an interactionbetween said additive and said further additive to form an intermetallicfilm.
 25. The process as in claim 16 further comprising the step (g) offorming a wiring pattern within said copper-containing film.
 26. Aprocess for forming a barrier film, comprising the steps of:(a) formingan alloy seed layer at least indirectly on a substrate; (b) forming acopper seed layer on said alloy seed layer, said copper seed layerincluding an exposed surface; (c) contacting said exposed surface withan electroplating solution and mechanically removing said electroplatingsolution from said surface within an oxygen environment, therebyroughening said exposed surface; (d) laminating an impurity film ontosaid exposed surface by immersing said substrate in said electroplatingsolution, said impurity film including copper and an impurity; (e)electrodepositing a copper-containing film onto said impurity film; and(f) forming a barrier material by annealing said substrate to urge aninterdiffusion between said alloy seed layer and said impurity.
 27. Theprocess as in claim 26, wherein said alloy seed layer is formed by oneof evaporation, sputtering, co-sputtering, immersion plating, orelectroplating.
 28. The process as in claim 26, wherein said copper seedlayer is formed by one of sputtering or chemical vapor deposition. 29.The process as in claim 26, wherein said annealing takes place at atemperature within the range of 100° C. to 550° C. and for a time withinthe range of 30 minutes to 180 minutes.
 30. The process as in claim 26,wherein said annealing is conducted in an inert atmosphere comprisingone of air and nitrogen.
 31. The process as in claim 26, wherein saidalloy seed layer comprises copper and at least one of chromium, indium,titanium, and tantalum.
 32. The process as in claim 26, wherein saidbarrier material comprises one of Cu(O), CuTi(O), CuCr(O) or theirassociated complexes with nitrogen, carbon, and sulfur.